Many heat exchangers of the type described above are in use for extracting heat from flue gases, such as in an electric power generation plant. The heat exchanger housings have circumferentially opposed sections, one for conducting flue gases through the core and the other for conducting air to be heated through the core. The core is rotatably driven so an element of the core is cyclically exposed first to the flue gas, then to the air to be heated, whereby heat is transferred while the hot and cold streams remain largely separated.
Apparatus designed for cleaning the cores of such heat exchangers and similar structures is well known to the art. Such core cleaners are used to periodically purge the heat exchangers of foreign matter such as fly ash corrosion, and the like that can seriously reduce the efficiency of a heat exchanger. Drive means are sometimes provided for such core cleaners to pass a nozzle or other concentrated source of pressurized cleaning fluid over one end of the core, allowing the cleaning fluid to enter and clean each passage in the core.
In heat exchangers of the type previously specified, the problem of causing a nozzle to travel circumferentially with respect to the core assembly can be solved by fixing the nozzle and rotating the core assembly with its built-in drive. But the problem remains of providing means to move the nozzle radially so that passages positioned at any radius from the central axis of the core assembly can be subjected to the action of the cleaning nozzle. The prior art has recognized this problem, but no solution to date has been completely satisfactory.
Other problems not solved by the prior art are the need in known cleaning methods to remove the end seals of the core assembly and other parts which can be damaged during cleaning; the prior need either to partially disassemble the heat exchanger to place a temporary cleaning device in it or to permanently mount a cleaning device in the hostile environment of the heat exchanger; the problem of providing a cleaning device which is adaptable for use in differently sized heat exchangers; and the problem of failure to clean each passage uniformly without wasting cleaning fluid.